<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        #test-by-a a:link {
            color: green;
        }

        #test-by-a a:hover {
            color: yellow;
        }

        #test-by-a a:active {
            color: red;
        }

        #test-by-a a:visited {
            color: purple;
        }
    </style>

    <style type="text/css">
        #test-by-focus input:focus {
            border: 1px solid blue;
        }
    </style>
</head>
<body>

<section id="test-by-a">
    <a href="http://www.baidu.com">百度</a>
</section>

<section id="test-by-focus">
    <label>
        <input type="text"/>
        <input type="text"/>
    </label>
</section>
</body>
</html>